Staphylococcus aureus esxA

Staphylococcus aureus esxA is a secreted virulence protein of Staphylococcus aureus, belonging to the ESAT-6/CFP-10 protein family. It is transported out of the bacterium via the Type VII secretion system, a key pathway for delivering virulence factors. EsxA plays critical roles in bacterial pathogenesis: it disrupts the membranes of host phagocytes (like macrophages), allowing Staphylococcus aureus to escape from phagosomes-vesicles that trap and attempt to kill the bacterium. This escape enables the bacterium to replicate freely in host cell cytoplasm. Additionally, esxA modulates host immune responses by suppressing the activation of immune cells and reducing pro-inflammatory cytokine production, creating a favorable environment for bacterial survival. Its conservation across most virulent Staphylococcus aureus strains and essential role in invasive infections make it a promising target for vaccines and novel antibacterial drugs; inhibiting esxA could block phagosome escape and restore host immune clearance.